The invention relates, in the first instance, to a method of operating a hydraulic pressing unit, in particular manual pressing unit, it being the case that the pressing unit has a hydraulic pump, a moving part, a stationary part and a non-return valve, that, furthermore, the moving part is displaced into a pressing position by the build-up of a hydraulic pressure and the non-return valve moves automatically into an open position only in the presence of a predetermined hydraulic pressure corresponding to a pressing pressure, and that, furthermore, the moving part is configured for moving back automatically from the pressing position into an end position under the action of a restoring spring and the non-return valve is configured only to close once the moving part has reached the end position.
As far as the prior art is concerned, you are referred to the applicant""s WO 99/19947.
In the case of the known unit, such a method has already been realized to great advantage and has enjoyed widespread use. It is usually also the case that the configuration is advantageous and satisfactory. However, there are some cases in which it is desirable to stop the moving part early without the displacement of the moving part into the end position being obstructed in other cases. It is thus an object to provide a hydraulic manual pressing unit which allows the moving part to be stopped optionally in position.
For this purpose, the invention proposes that, before the end position of the moving part is reached, the non-return valve is subject to the action of a corresponding closure force.
This can take place optionally in any position of the moving part by means of acting directly on the non-return valve, if appropriate also by hand. For this purpose, it is advantageously possible to make use of the fact that the non-return valve has an actuating section extending outside the unit. In the simplest case, the user can subject said actuating section to the necessary force, for example, by hand. It is thus readily possible to interrupt the return in any position of the moving part. It is also easily possible for this means of action for the user to be shifted, if appropriate via lever transmission, into the region of the unit handle, for example to where, if appropriate via a further button, the triggering button of the unit is also disposed.
More specifically, it is also possible to provide that the non-return valve is arrested until a pre-selected or predetermined return position of the moving part has been reached. This makes it possible to provide the abovementioned closure force, for example, by means of a high-force restoring spring acting on the non-return valve. As the pressing pressure is reached, this high-force restoring spring is automatically moved into a prestressing position, by the hydraulic pressure also acting on the moving part, and immediately arrested there. The non-return valve is thus exposed to this force, in principle, during return of the moving part, but the arresting means absorbs this force until it is released by the user by actuation, or by the unit itself, when a predetermined return position of the moving part is reached. The action on the non-return valve takes place correspondingly by release of a previously stored closure force.
In one configuration of the known unit mentioned in the introduction, it is also possible for the non-return valve to be formed magnetically and for the abovementioned force to be produced by an electromagnet being switched on at a given point in time. It is then possible for the electromagnet either to pull the non-return valve into its closed position or, with equal poles located opposite one another, to push the non-return valve into its closed position. Furthermore, it is also possible to carry out electromechanical arresting. In this case an electrical actuating part, for example once again an electromagnet, pushes a mechanical arresting part into the displacement path of the non-return valve, the open position of the latter. In the same way, this locking can then be withdrawn again by electrical actuation.
The magnetic or electromagnetic action, however, clearly does not, or in any case does not necessarily, take place by the release of a previously stored closure force. Rather, it takes place by supplying power to a corresponding electromagnetic or electromechanical arrangement.
It is recommended to integrate the means for actuating the locking, or releasing the locking, of the non-return valve and/or the actuating means for producing the necessary closure force, irrespective of the position of the return part, in the actuating handle of the unit, said handle being present in any case. This is done straightforwardly for example, as has already been mentioned in principle, via a mechanical lever device which acts on the end of the non-return valve.
In a further-developed configuration, it may be provided that the actuating button for starting the electric motor, or the hydraulic pump connected thereto, is also provided, at the same time, with a button for acting on the locking part of the non-return valve.
In a further actual embodiment, it is possible for the triggering button to be suspended in a lever-like manner and to be provided with a locking pin which can be moved back counter to spring force and, for its part, engages beneath a locking part, adjustable counter to spring force and acting on the non-return valve, and can also run over the same again.
The invention proposes, as subject matter, a hydraulic pressing unit having a hydraulic piston running in a cylinder, it being possible for the hydraulic piston to be moved back counter to the force of a restoring spring.
In order to achieve the object of providing a more advantageous pressing unit, in particular manual pressing unit, the invention proposes that it is possible to stop the return of the hydraulic piston before it reaches the starting position by a triggering device, acting on the non-return valve.
In a first embodiment, this may be achieved in that the triggering device comprises a pulling or pushing part connected to the non-return valve. The pulling or pushing part passes through not just the valve cylinder but also a housing wall which also encloses the unit, usually outside the valve. It can be subjected, for example, to manual action. If, in the case of the configuration in accordance with WO 99/19947, the disclosure contents of this document are hereby included in full in the disclosure of the present application, also for the purpose of incorporating features of the related application in claims of the present application, the non-return valve is pulled or pushed into the closed position during the return of the moving part, the hydraulic volume is prevented from decreasing further. The moving part comes to a standstill. Upon renewed triggering actuation of the electrical motor, the moving part can then be moved, from the location at which it has been stopped, into the closed position again.
As far as a pulling part is concerned, it is possible, for example, for the tip of the closure valve to be formed as a rod passing through the housing, obviously with corresponding sealing. In the case of the known unit, an extension of the non-return valve which is oriented in the opening direction and passes through the housing wall is configured as the pulling part. Via a rocker part which is connected thereto, and ultimately only passes through the outer housing covering, it can be utilized for opening the non-return valve. This extension is then configured as a pushing part. It has a freely accessible end region on which it is possible to act in order to close the non-return valve.
In a further configuration, it may also be provided that an electromagnet acts on the non-return valve. In a fair number of embodiments, such a manual pressing unit is also operated by a storage battery, or else by direct connection to an electricity supply, for example in an assembly building. This may be used in order to provide an electromagnet associated with the non-return valve. Depending on the polarity in relation to the non-return valve, the electromagnet can either push or pull said valve into the closed position.
In a further configuration, it may be provided that the non-return valve is subjected to the action of a prestressing force which is sufficient for displacement into the closed position at any point in time at which the moving part is moving back. This may be important and advantageous in the first instance, irrespective of possible displacement into the closed position at any point in time of the return of the moving part, just from the point of view that the automatic return of the moving part depends as little as possible on the pressure which is produced by the compression spring acting on the non-return valve, this being so even in the case of the non-return valve being independent of the pressure produced by the restoring spring.
In respect of this aspect, the invention proposes, in the first instance, that the open position of the non-return valve is arrested until a predetermined return position of the moving part has been reached. According to the invention it is provided that the open position of the non-return valve is arrested mechanically, specifically until the moving part has been moved into its starting position or a desired return position of the moving part has been reached.
In one configuration, it may be provided that the non-return valve has a latching socket in which an arresting protrusion engages for the arresting operation. The latching socket is suitably provided to the rear of the active piston surface of the non-return valve.
The arresting protrusion which moves into the latching socket is suitably subjected to spring prestressing.
As far as the arresting protrusion is concerned, a separate disengaging part is provided and moves the arresting protrusion out of the latching socket, this in dependence on given mechanical conditions or pressure conditions, and as explained in more detail hereinbelow.
The disengaging part can interact with a ramp of the arresting protrusion. For this purpose, a conical surface or some other ramp-like surface is suitably formed on the arresting protrusion. The disengaging part has a surface which corresponds thereto. A sliding wedge action is produced as a result.
According to a first embodiment, the moving part can act mechanically on the disengaging part. The moving part is usually a piston of the pressing unit. The disengaging part projects, for mechanical activation, in the displacement direction of the piston, so that the piston or the moving part, as it is displaced, mechanically actuates the disengaging part in a certain section of the displacement path, preferably at the end of the displacement path.
According to a second embodiment, the disengaging part may be subjected to spring prestressing. The spring prestressing drives the disengaging part into the disengagement position. The spring prestressing is exceeded by the, hydraulic pressure which prevails during pressing and return of the moving part. It is only once the moving part is at a standstill that the hydraulic pressure drops to the extent where the disengaging part, as a result of the spring prestressing to which it is subjected, moves out of a movement path of the arresting protrusion, which then, because it itself is subjected to spring prestressing, moves out of the latching socket of the non-return valve and thus releases the latter for closure.
The disengaging part may also be used in order to make it possible for the arresting protrusion to be lifted out of the arresting position by manual actuation. For this purpose, in a simple version, the arresting protrusion is guided out of the housing at one end and, there, pulled out of the arresting position by hand, for example, counter to its prestressing force. The disengaging part is then the rearwardly projecting section of the arresting protrusion.
In this respect, however, it is also possible to provide a separate disengaging part which, at least over a certain movement region, interacts in a positively locking manner with the arresting protrusion and is, for example, in the form of a rocker. When the disengaging part is moved, the arresting protrusion is then inevitably also withdrawn from its arresting position. More specifically, it is also possible for the disengaging part, for this purpose, to be coupled to an actuating switch of the unit, for example to the triggering or starting switch of the unit, for example such that further actuating of the starting switch results in the arresting protrusion being withdrawn from the arresting position and thus in the moving part being stopped. Subsequent actuation of the starting switch then results, once again, in the electric motor starting up and the pump operating, so that a new pressing process begins.